A7330MP8R [AITSEMI]
DC-DC CONVERTER BUCK SENSORLESS CC/CV;
| 型号： | A7330MP8R |
| 厂家： | 
AiT Semiconductor |
| 描述： | DC-DC CONVERTER BUCK SENSORLESS CC/CV DC-DC转换器 |
| 文件： | 总14页 (文件大小：304K) |
| 中文： | 中文翻译 | 下载： | 下载PDF数据表文档文件 |
A7330
DC-DC CONVERTER BUCK (STEP-DOWN)
SENSORLESS CC/CV
AiT Semiconductor Inc.
www.ait-ic.com
DESCRIPTION
FEATURES
A7330 is a wide input voltage, high efficiency
step-down DC/DC converter that operates in either
CV (Constant Output Voltage) mode or CC(Constant
Output Current) mode. A7330 provides up to 3.5A
output current at 125kHz switching frequency.
A7330 integrates control scheme to achieve
high-accuracy constant current control without the
expensive, high accuracy current sense resistor. It
also integrates adaptive gate drive to achieve
excellent EMI performance passing EN55022 Class
B EMC standard without adding additional EMI
components while maintaining high conversion
efficiency.
Up to 3.5A output current
125kHz Switching Frequency Eases EMI Design
91% Efficiency (VOUT=5V@2.4A at VIN=12V)
Resistor Programmable for Output Cable Drop
Compensation
Cycle-by-Cycle Current Limit, Output Over
Voltage Protect, Thermal Shutdown, Input Under
Voltage Lockout
Integrated Soft Start
±7.5% CC Accuracy
±2% CV Accuracy
High-Side RDSON 50mΩ
Available in PSOP8 Package
Protection features include cycle-by-cycle current
limit, thermal shutdown, and frequency foldback at
short circuit.
APPLICATION
Car Charger/ Adaptor
General-Purpose CV/CC Power Supply
Rechargeable Portable Devices
The A7330 is available in PSOP8 package.
ORDERING INFORMATION
TYPICAL APPLICATION
Package Type
Part Number
A7330MP8R
A7330MP8VR
PSOP8
SPQ: 3,000pcs/Reel
MP8
V: Halogen free Package
R: Tape & Reel
Note
AiT provides all RoHS products
REV1.0
- JAN 2016 RELEASED -
- 1 -
A7330
DC-DC CONVERTER BUCK (STEP-DOWN)
SENSORLESS CC/CV
AiT Semiconductor Inc.
www.ait-ic.com
PIN DESCRIPTION
Top View
Pin #
1
Symbol
HSB
Function
High Side Bias Pin. This provides power to the internal high-side MOSFET
gate driver. Connect a 22nF capacitor from HSB pin to SW pin.
Power Supply Input. Bypass this pin with a 10μF ceramic capacitor to GND,
placed as close to the IC as possible.
2
3
IN
SW
Power Switching Output to External Inductor.
Ground. Connect this pin to a large PCB copper area for best heat dissipation.
Return FB, COMP, and ISET to this GND, and connect this GND to power GND
at a single point for best noise immunity.
4
GND
Feedback Input. The voltage at this pin is regulated to 800mV. Connect to the
resistor divider between output and GND to set the output voltage.
Error Amplifier Output. This pin is used to compensate the converter.
OVP input. If the voltage at this pin exceeds 0.8V, the IC shuts down high side
switch. There is a 2μA pull-up current at this pin.
5
6
7
FB
COMP
OVP
Output Current Setting Pin. Connect a resistor from ISET to GND to program
the output current.
8
ISET
Exposed
Pad
Heat Dissipation Pad. Connect this exposed pad to large ground copper area
with copper and vias.
REV1.0
- JAN 2016 RELEASED -
- 2 -
A7330
DC-DC CONVERTER BUCK (STEP-DOWN)
SENSORLESS CC/CV
AiT Semiconductor Inc.
www.ait-ic.com
ABSOLUTE MAXIMUM RATINGS
VIN, IN to GND
-0.3V ~ 32V
-1V ~ VIN+1V
VSW-0.3V ~ VSW+7V
-0.3V ~ 6V
SW to GND
VGATE, HSB to GND
FB, ISET, COMP to GND
TSTG, Storage Temperature Range
TJ, Operating Junction Temperature
ESD Human Model
-40℃ ~ 150℃
-40℃ ~ 150℃
4000V
Stress beyond above listed “Absolute Maximum Ratings” may lead permanent damage to the device. These are stress ratings only and
operations of the device at these or any other conditions beyond those indicated in the operational sections of the specifications are not
implied. Exposure to absolute maximum rating conditions for extended periods may affect device reliability.
REV1.0
- JAN 2016 RELEASED -
- 3 -
A7330
DC-DC CONVERTER BUCK (STEP-DOWN)
SENSORLESS CC/CV
AiT Semiconductor Inc.
www.ait-ic.com
ELECTRICAL CHARACTERISTICS
Parameter
Input Voltage
Conditions
Min.
10
Typ.
Max.
30
Unit
V
Input Voltage Surge
32
V
VIN UVLO Turn-On Voltage
VIN UVLO Hysteresis
Standby Supply Current
Feedback Voltage
Input Voltage Rising
Input Voltage Falling
VFB=1V
9.0
9.3
1.1
9.7
V
V
0.88
800
500
1.4
mA
mV
μs
785
815
Internal Soft-Start Time
VFB=VCOMP=0.8V
Error Amplifier Transconductance
650
μA/V
ΔICOMP=±10μA
Error Amplifier DC Gain
Switching Frequency
Foldback Switching Frequency
Maximum Duty Cycle
Minimum On-Time
4000
125
18
V/V
kHz
kHz
%
VFB=0.8V
VFB=0V
85
300
ns
COMP to Current Limit
Transconductance
VCOMP=1.7V
3.47
6.4
A/V
A
Secondary Cycle-by-Cycle Current
Limit
Slope Compensation
ISET Voltage
Duty=DMAX
3
1
A
V
ISET to IOUT DC Room Temp Current
Gain
IOUT/ISET，RISET=25kΩ
100000
A/A
CC Controller DC Accuracy
OVP Pin Lock Voltage
OVP Pin Unlock Voltage
High-Side Switch ON-Resistance
Thermal Shutdown Temperature
Thermal Shutdown Temperature
Hysteresis
R
ISET=24.9kΩ, VOUT=4.0V
3600
0.833
0.764
45
mA
V
OVP Pin Voltage Rising
OVP Pin Voltage Falling
Not Include Bonding Wire
Temperature Rising
V
mΩ
℃
151
Temperature Falling
22
℃
REV1.0
- JAN 2016 RELEASED -
- 4 -
A7330
DC-DC CONVERTER BUCK (STEP-DOWN)
SENSORLESS CC/CV
AiT Semiconductor Inc.
www.ait-ic.com
BLOCK DIAGRAM
REV1.0
- JAN 2016 RELEASED -
- 5 -
A7330
DC-DC CONVERTER BUCK (STEP-DOWN)
SENSORLESS CC/CV
AiT Semiconductor Inc.
www.ait-ic.com
DETAILED INFORMATION
Application Information
CV/CC Loop Regulation
As seen in Function Block Diagram, the A7330 is a peak current mode pulse width modulation (PWM)
converter with CC and CV control. The converter operates as follows:
A switching cycle starts when the falling edge of the Oscillator clock output causes the High-Side Power
Switch to turn on and the Low-Side Power Switch to turn off. With the SW side of the inductor now connected
to IN, the inductor current ramps up to store energy in the magnetic field. The inductor current level is
measured by the Current Sense Amplifier and added to the Oscillator ramp signal. If the resulting summation
is higher than the COMP voltage, the output of the PWM Comparator goes high. When this happens or when
Oscillator clock output goes high, the High-Side Power Switch turns off.
At this point, the SW side of the inductor swings to a diode voltage below ground, causing the inductor current
to decrease and magnetic energy to be transferred to output. This state continues until the cycle starts again.
The High-Side Power Switch is driven by logic using HSB as the positive rail. This pin is charged to VSW+5V
when the Low-Side Power Switch turns on. The COMP voltage is the integration of the error between FB input
and the internal 0.8V reference. If FB is lower than the reference voltage, COMP tends to go higher to
increase current to the output. Output current will increase until it reaches the CC limit set by the ISET resistor.
At this point, the device will transition from regulating output voltage to regulating output current, and the
output voltage will drop with increasing load. The Oscillator normally switches at 125kHz. However, if FB
voltage is less than 0.6V, then the switching frequency decreases until it reaches a typical value of 18kHz at
VFB = 0.15V.
Over Voltage Protection
The A7330 has an OVP pin. If the voltage at this pin exceeds 0.8V, the IC shuts down high-side switch. There
is a 2μA pull-up current at this pin.
Thermal Shutdown
The A7330 disables switching when its junction temperature exceeds 151℃ and resumes when the
temperature has dropped by 22℃.
Output Voltage Setting
The figure shows the connections for setting the output voltage.
REV1.0
- JAN 2016 RELEASED -
- 6 -
A7330
DC-DC CONVERTER BUCK (STEP-DOWN)
SENSORLESS CC/CV
AiT Semiconductor Inc.
www.ait-ic.com
Select the proper ratio of the two feedback resistors RFB1 and RFB2 based on the output voltage. Adding a
capacitor in parallel with RFB1 helps the system stability. Typically, use RFB2≈10kΩ and determine RFB1 from
the following equation:
VOUT
0.8V
R
FB1=RFB2
−1
CC Current Setting
A7330 constant current value is set by a resistor connected between the ISET pin and GND. The CC output
current is linearly proportional to the current flowing out of the ISET pin. The voltage at ISET is roughly 1V and
the current gain from ISET to output is roughly 100000 (100mA/1μA). To determine the proper resistor for a
desired current, please refer to figure below.
Output Current vs. RISET
CC Current Line Compensation
When operating at constant current mode, the current limit increase slightly with input voltage. For wide input
voltage applications, a resistor RC may be added to compensate line change and keep output high CC
accuracy, as shown figure below.
REV1.0
- JAN 2016 RELEASED -
- 7 -
A7330
DC-DC CONVERTER BUCK (STEP-DOWN)
SENSORLESS CC/CV
AiT Semiconductor Inc.
www.ait-ic.com
Inductor Selection
The inductor maintains a continuous current to the output load. This inductor current has a ripple that is
dependent on the inductance value.
Higher inductance reduces the peak-to-peak ripple current. The trade off for high inductance value is the
increase in inductor core size and series resistance, and the reduction in current handling capability. In
general, select an inductance value L based on ripple current requirement:
VOUT x (VIN − VOUT)
L =
VIN x∫SW x ILOADMAX x KRIPPLE
Where VIN is the input voltage, VOUT is the output voltage, fSW is the switching frequency, ILOADMAX is the
maximum load current, and KRIPPLE is the ripple factor. Typically, choose KRIPPLE=30% to correspond to the
peak-to-peak ripple current being 30% of the maximum load current.
With a selected inductor value the peak-to-peak inductor current is estimated as:
V
OUT x (VIN − VOUT)
ILPK-PK
=
V
IN x ∫SW xL
The peak inductor current is estimated as:
1
2
ILPK = ILOADMAX
+
ILPK-PK
The selected inductor should not saturate at ILPK
.
The maximum output current is calculated as:
1
2
IOUTMAX = ILIM
-
ILPK-PK
ILIM is the internal current limit, which is typically 5.4A, as shown in Electrical Characteristics Table.
REV1.0
- JAN 2016 RELEASED -
- 8 -
A7330
DC-DC CONVERTER BUCK (STEP-DOWN)
SENSORLESS CC/CV
AiT Semiconductor Inc.
www.ait-ic.com
External High Voltage Bias Diode
It is recommended that an external High Voltage Bias diode be added when the system has a 5V fixed input
or the power supply generates a 5V output. This helps improve the efficiency of the regulator. The High
Voltage Bias diode can be a low cost one such as IN4148 or BAT54, as figure shown below.
This diode is also recommended for high duty cycle operation and high output voltage applications.
Input Capacitor
The input capacitor needs to be carefully selected to maintain sufficiently low ripple at the supply input of the
converter. A low ESR capacitor is highly recommended. Since large current flows in and out of this capacitor
during switching, its ESR also affects efficiency.
The input capacitance needs to be higher than 10μF.The best choice is the ceramic type, however, low ESR
tantalum or electrolytic types may also be used provided that the RMS ripple current rating is higher than 50%
of the output current. The input capacitor should be placed close to the IN and G pins of the IC, with the
shortest traces possible. In the case of tantalum or electrolytic types, they can be further away if a small
parallel 0.1μF ceramic capacitor is placed right next to the IC.
Output Capacitor
The output capacitor also needs to have low ESR to keep low output voltage ripple. The output ripple voltage
is:
V
IN
VRIPPLE = IOUTMAX x KRIPPLE x RESR
+
28 x ∫SW2 LC OUT
Where IOUTMAX is the maximum output current, KRIPPLE is the ripple factor, RESR is the ESR of the output
capacitor, fSW is the switching frequency, L is the inductor value, and COUT is the output capacitance. In the
case of ceramic output capacitors, RESR is very small and does not contribute to the ripple. Therefore, a lower
capacitance value can be used for ceramic type. In the case of tantalum or electrolytic capacitors, the ripple is
dominated by RESR multiplied by the ripple current. In that case, the output capacitor is chosen to have
sufficiently low ESR.
For ceramic output capacitor, typically choose a capacitance of about 22μF. For tantalum or electrolytic
REV1.0
- JAN 2016 RELEASED -
- 9 -
A7330
DC-DC CONVERTER BUCK (STEP-DOWN)
SENSORLESS CC/CV
AiT Semiconductor Inc.
www.ait-ic.com
capacitors, choose a capacitor with less than 50mΩ ESR.
Rectifier Diode
Use a Schottky diode as the rectifier to conduct current when the High-Side Power Switch is off. The Schottky
diode must have current rating higher than the maximum output current and a reverse voltage rating higher
than the maximum input voltage.
Stability Compensation
The feedback loop of the IC is stabilized by the components at the COMP pin, as shown in figure below.
NOTE ①: CCOMP2 is needed only for high ESR output capacitor
The DC loop gain of the system is determined by the following equation:
0.8V
AVDC
=
x AVEA x GCOMP
I
OUT
The dominant pole P1 is due to CCOMP
:
G
EA
∫
P1
=
2πAVEA
C
COMP
The second pole P2 is the output pole:
I
OUT
∫
=
P2
2πVOUT
C
OUT
The first zero Z1 is due to RCOMP and CCOMP
:
1
∫
Z1
=
2πRCOMP
CCOMP
And finally, the third pole is due to RCOMP and CCOMP2 (if CCOMP2 is used):
1
∫
=
P3
2πRCOMPCCOMP2
The following steps should be used to compensate the IC:
REV1.0
- JAN 2016 RELEASED -
- 10 -
A7330
DC-DC CONVERTER BUCK (STEP-DOWN)
SENSORLESS CC/CV
AiT Semiconductor Inc.
www.ait-ic.com
STEP 1. Set the cross over frequency at 1/10 of the switching frequency via RCOMP
:
2πVOUTCOUT∫SW
10GEAGCOMP x 0.8V
RCOMP
=
=5.17 x 107VOUTCOUT………… (Ω)
STEP 2. Set the zero fZ1 at 1/4 of the cross over frequency. If RCOMP is less than 15kΩ, the equation for CCOMP
is:
2.83 x105
CCOPM
=
……………….(F)
RCOMP
If RCOMP is limited to 15kΩ, then the actual cross over frequency is 6.58 / (VOUTCOUT). Therefore:
COMP = 6.45 x 10-6VOUTCOUT………(F)
C
STEP 3. If the output capacitor’s ESR is high enough to cause a zero at lower than 4 times the cross over
frequency, an additional compensation capacitor CCOMP2 is required. The condition for using CCOMP2 is:
1.77x10−6
OUT
RESRCOUT
≥
Min
,0.06 x V
………… (Ω)
COUT
And the proper value for CCOMP2 is:
C
OUT
R
COMP
ESRCOUT
CCOMP2
=
R
Though CCOMP2 is unnecessary when the output capacitor has sufficiently low ESR, a small value CCOMP2 such
as 100pF may improve stability against PCB layout parasitic effects.
CC Loop Stability
The constant-current control loop is internally compensated over the 2000mA-3500mA output range. No
additional external compensation is required to stabilize the CC current.
Output Cable Resistance Compensation
To compensate for resistive voltage drop across the charger's output cable, the A7330 integrates a simple,
user-programmable cable voltage drop compensation using the impedance at the FB pin. Use the curve in
Figure 1 to choose the proper feedback resistance values for cable compensation. RFB1 is the high side
resistor of voltage divider.
REV1.0
- JAN 2016 RELEASED -
- 11 -
A7330
DC-DC CONVERTER BUCK (STEP-DOWN)
SENSORLESS CC/CV
AiT Semiconductor Inc.
www.ait-ic.com
Delta Output Voltage vs. Output Current
In the case of high RFB1 used, the frequency compensation needs to be adjusted correspondingly. As show in
Figure 2, adding a capacitor in paralleled with RFB1 or increasing the compensation capacitance at COMP pin
helps the system stability.
PC Board Layout Guidance
When laying out the printed circuit board, the following checklist should be used to ensure proper operation of
the IC.
1） Arrange the power components to reduce the AC loop size consisting of CIN, IN pin, SW pin and the
schottky diode.
2） Place input decoupling ceramic capacitor CIN as close to IN pin as possible. CIN is connected power GND
with vias or short and wide path.
3） Return FB, COMP and ISET to signal GND pin, and connect the signal GND to power GND at a single
point for best noise immunity. Connect exposed pad to power ground copper area with copper and vias.
4） Use copper plane for power GND for best heat dissipation and noise immunity.
5） Place feedback resistor close to FB pin.
6） Use short trace connecting HSB-CHSB-SW loop.
REV1.0
- JAN 2016 RELEASED -
- 12 -
A7330
DC-DC CONVERTER BUCK (STEP-DOWN)
SENSORLESS CC/CV
AiT Semiconductor Inc.
www.ait-ic.com
PACKAGE INFORMATION
Dimension in PSOP8 Package (Unit: mm)
Millimeters
Inches
Max
Symbol
Min
Max
Min
A
A1
A2
b
1.350
0.100
1.350
0.330
0.170
4.700
3.202
3.800
5.800
2.313
1.750
0.250
1.550
0.510
0.250
5.100
3.402
4.000
6.200
2.513
0.053
0.004
0.053
0.013
0.006
0.185
0.126
0.150
0.228
0.091
0.069
0.010
0.061
0.020
0.010
0.200
0.134
0.157
0.244
0.099
c
D
D1
E
E1
E2
e
1.270(BSC)
0.050(BSC)
L
0.400
0°
1.270
8°
0.016
0°
0.050
8°
θ
REV1.0
- JAN 2016 RELEASED -
- 13 -
A7330
DC-DC CONVERTER BUCK (STEP-DOWN)
SENSORLESS CC/CV
AiT Semiconductor Inc.
www.ait-ic.com
IMPORTANT NOTICE
AiT Semiconductor Inc. (AiT) reserves the right to make changes to any its product, specifications, to
discontinue any integrated circuit product or service without notice, and advises its customers to obtain the
latest version of relevant information to verify, before placing orders, that the information being relied on is
current.
AiT Semiconductor Inc.'s integrated circuit products are not designed, intended, authorized, or warranted to
be suitable for use in life support applications, devices or systems or other critical applications. Use of AiT
products in such applications is understood to be fully at the risk of the customer. As used herein may involve
potential risks of death, personal injury, or server property, or environmental damage. In order to minimize
risks associated with the customer's applications, the customer should provide adequate design and
operating safeguards.
AiT Semiconductor Inc. assumes to no liability to customer product design or application support. AiT
warrants the performance of its products of the specifications applicable at the time of sale.
REV1.0
- JAN 2016 RELEASED -
- 14 -
©2020 ICPDF网 联系我们和版权申明